Multiple-input and multiple-output (MIMO) detection in wireless communications

Abstract

Introduced here is at least one technique to better estimate interference at a receiver. The technique includes receiving a plurality of reference signals, which each have information indicative of noise. Thus, the technique further includes, for each reference signal, determining a noise estimation and determining a distance metric and log-likelihood ratio (LLR) of the noise estimation. Once the distance metric and LLR of each reference signal is determined, the receiver can determine a final LLR based on the distance metric and LLR of each reference signal. In this manner, a final LLR is determined. This technique can be applied by any device operating on MIMO technology.

What is claimed is: 
     
       1. A method for improving noise estimation at a receiver, the method comprising:
 receiving a plurality of reference signals; 
 for a given reference signal:
 determining a noise estimation; and 
 determining a distance metric and a log-likelihood ratio (LLR) of the noise estimation; and 
 
 determining a final LLR based on the distance metric and the LLR of each noise estimation; 
 wherein determining the final LLR further comprises: 
 combining the LLRs of at least two noise estimations; or 
 selecting the LLR of a particular noise estimation based on the distance metric of the particular noise estimation; 
 wherein for a first reference signal of the plurality of reference signal, the noise estimation is a first noise estimation, the distance metric is a first distance metric, and the LLR is a first LLR; 
 for a second reference signal of the plurality of reference signals, the noise estimation is a second noise estimation, the distance metric is a second distance metric, and the LLR is a second LLR; 
 wherein the method further comprises: 
 determining a combined noise estimate, wherein determining the combined noise estimate comprises:
 combining the first LLR and the second LLR; or 
 determining that the second distance metric is nearer to a threshold value than the first distance metric; and determining the combined noise estimate according to the second noise estimation. 
 
 
     
     
       2. The method of  claim 1 , wherein determining the final LLR further comprises:
 determining whether the distance metric is greater than a threshold value. 
 
     
     
       3. The method of  claim 1 , wherein determining the distance metric and the LLR comprises:
 decomposing the noise estimate based on Cholesky decomposition techniques; and 
 applying sphere decoding techniques. 
 
     
     
       4. The method of  claim 3 , wherein the sphere decoding techniques include K-best, fixed complexity sphere decoding, and/or depth first sphere decoding. 
     
     
       5. The method of  claim 1 , wherein combining the LLRs of the at least two noise estimations further comprises:
 selecting the at least two noise estimations based on the distance metric of the at least two noise estimations. 
 
     
     
       6. The method of  claim 1 , wherein determining the noise estimation comprises:
 determining a covariance based on any of:
 interference from a transmitter, wherein the transmitter is connected to the receiver; 
 interference from every transmitter within a threshold distance; and/or 
 interference from a particular transmitter that the receiver is not connected to. 
 
 
     
     
       7. The method of  claim 6 , further comprising:
 for a first reference signal of the plurality of reference signals, determining a first noise estimation according to a first covariance, wherein the first covariance is based on the interference from the transmitter, wherein the transmitter is connected to the receiver. 
 
     
     
       8. The method of  claim 6 , further comprising:
 for a second reference signal of the plurality of reference signals, determining a second noise estimate according a second covariance, wherein the second covariance is based on the interference from every transmitter with the threshold distance. 
 
     
     
       9. The method of  claim 6 , further comprising:
 for a third reference signal of the plurality of reference signals, determining a third noise estimate according a third covariance, wherein the third covariance is based on the interference from the particular transmitter that the receiver is not connected to. 
 
     
     
       10. The method of  claim 1 , wherein the distance metric is based on a Euclidean Distance calculation and/or Manhattan Distance calculation. 
     
     
       11. The method of  claim 10 , wherein a first distance metric of a first noise estimation is based on the Euclidean Distance calculation, wherein a second distance metric of a second noise estimation is based on the Manhattan Distance calculation. 
     
     
       12. The method of  claim 1 , wherein the plurality of reference signals is from a transmitter that the receiver is connected to or from multiple transmitters within a threshold distance of the receiver. 
     
     
       13. The method of  claim 1 , wherein the receiver is operating in multiple-input and multiple output (MIMO) technology. 
     
     
       14. A method comprising:
 receiving a reference signal; 
 determining a noise estimation of the reference signal; 
 determining a distance metric and a log-likelihood ratio (LLR) of the determined noise estimation, wherein determining the distance metric and the LLR comprises:
 decomposing the noise estimation based on Cholesky decomposition techniques; and 
 applying sphere decoding techniques; and 
 
 determining a final LLR based on the distance metric and the LLR of the noise estimation,
 wherein determining the final LLR further comprises: 
 combining the LLR of the noise estimation with an LLR of another noise estimation; or 
 selecting the LLR of the noise estimation based on the distance metric of the noise estimation; 
 
 wherein the reference signal is a first reference signal, the noise estimation is a first noise estimation, the distance metric is a first distance metric, and the LLR is a first LLR, the method further comprising: 
 receiving a second reference signal; 
 determining a second noise estimation of the second reference signal; 
 determining a second distance metric and a second (LLR) of the second noise estimation; and 
 determining a combined noise estimate, wherein determining the combined noise estimate comprises:
 combining the first LLR and the second LLR; or 
 determining that the second distance metric is nearer to a threshold value than the first distance metric; and determining the combined noise estimate according to the second noise estimation. 
 
 
     
     
       15. The method of  claim 14 , wherein the method is performed by a receiver, and wherein the reference signal is from a transmitter that the receiver is connected to. 
     
     
       16. A receiver comprising:
 a receiver operable to receive a plurality of reference signals; and 
 a processor operable to:
 for a given reference signal of the plurality of reference signals:
 determining a noise estimation; and 
 determine a distance metric and a log-likelihood ratio (LLR) of the noise estimation; and 
 
 determine a final LLR based on of the distance metric and the LLR of each noise estimation; 
 
 wherein the processor is further operable to: 
 combine the LLRs of at least two noise estimations; or 
 select the LLR of a particular noise estimation based on the distance metric of the particular noise estimation; 
 wherein for a first reference signal of the plurality of reference signal, the noise estimation is a first noise estimation, the distance metric is a first distance metric, and the LLR is a first LLR; 
 for a second reference signal of the plurality of reference signals, the noise estimation is a second noise estimation, the distance metric is a second distance metric, and the LLR is a second LLR; 
 wherein the processor is further operable to: 
 determine a combined noise estimate, wherein determining of the combined noise estimate comprises:
 combining the first LLR and the second LLR; or 
 determining that the second distance metric is nearer to a threshold value than the first distance metric; and determining the combined noise estimate according to the second noise estimation. 
 
 
     
     
       17. The receiver of  claim 16 , wherein the receiver is operating in multiple-input and multiple output (MIMO) technology, and the plurality of reference signals are from one or more transmitters. 
     
     
       18. The receiver of  claim 17 , wherein the receiver is connected to the one or more transmitters.